Winemaking Flashcards
Why do late harvest/botrytised grapes get “stuck” fermentation
Typically contain more fructose than glucose. Yeasts quickly consume glucose but struggle to metabolize fructose
*both are the main fermentable sugars
Device to measure sugar content in the field? In the winery?
Refractometer
Hydrometer
Brix
a measure of the amount of dissolved solids in a liquid via its specific gravity
*used to measure sugar dissolved in liquid
TA
Tirtratable acidity: the perception of sour
*higher = more sour
typically in the range of 4 to 9 grams per liter tartaric acid equivalents
pH in wine
Wine is usually around pH 3 or 4 (logarithmic - so 3 has 10x more acidity than 4)
A measure of the concentration of hydrogen ions (or protons) in a solution
Total Acidity
A measure of organic acids
Catechins
small polyphenols extracted from skins and seeds; responsible for bitterness in wine
Reductive approach to fruit processing/handling
Goal: preserve aromatics / freshness, fruit, floral flavors, prevent browning
Method: dry ice (carbon dioxide), inert gas, sulfur dioxide to protect must during processing
Purpose of intentionally oxidizing white wine must?
- juice turns brown initially but clarifies throughout fermentation.
*Susceptible compounds oxidize and are discarded as lees - finished wine is potentially less fruity but more resilient against post-fermentation oxidation
Sorting
*method: hand, shaker tables, optical sorters
*cluster sorting removes compromised bunches and MOG
*Berry sorting for de-stemmed fruit removes shot berries, stem, insects
Sorting for skin contact wines is more critical since they have more time to extract the bad stuff. Light/quick presses aren’t as critical.
Laccase
A particularly virulent oxidation enzyme produced by botrytis
* not deterred by sulfur dioxide or alcohol
Cluster vs. De-stemming in white winemaking
*de-stemmed and/or crushed fruit imparts more texture/skin influence
- whole cluster press = clear juice, few skin-derived compounds including phenolics that cause bitterness
** whole cluster is required for many sparkling wines since skin contact is undesirable
ABV inside carbonic maceration berries?
2% - then enzymes are denatured and fermentation stops
Stems in fermentation
Increase amounts of phenolic compounds, potassium
- often results in lighter colored, more tannic wines with higher pH and lower alcohol
Rosé methods
- Direct press: whole cluster, treated like white wine. Essentially a red wine made with no skin contact.
- Maceration/Saignée: quick maceration then juice is bled off. Red wine with very short skin contact.
- Blending: Rosé Champagne and few other styles
Saignée
Red wine technique - concentrates must
* juice is removed from red wine tank to increase proportion of skins to concentrate that wine
* this juice can become rosé - but since original purpose was red wine, it has a higher pH and more sugar so may require adjustment for balance
Cold Soak
Red wines held inoculated for days to weeks at cold temps
* fruit enzymes break down skins, starting extraction process
* populations of wild yeasts build (favored over Saccharomyces at cooler temps)
* some believe increases color extraction
Thermovinifcation
GOAL: accelerate extraction
WHY: saves tank space, fixes low quality fruit, denatures laccase in botrytised wine which prevents excessive oxidation
METHOD: 140 - 180º for 30min to 24hrs. Press directly after heating then fermentation commences
Little tannin extraction.
Flash Detente
GOAL: accelerate extraction
WHY: saves tank space, fixes low quality fruit, denatures laccase in botrytised wine which prevents excessive oxidation
METHOD: grapes rapidly brought to 185º then immediately cooled. Complete destruction on cellular level - looks like jam. Settled, drained, pressed, then fermented.
Little tannin extraction.
Press Cut
The separation of juice during the pressing process.
Free run, the press cut, and the hard press - as the press applies increasing pressure, the decision of when to separate the free run/mid from the heaviest press
- typically based on taste, looking for changes in aromatics, acidity, the level of oxidation, and tannnin extraction
Free run
juice liberated without application of pressure
* free run and light press are used interchangeably with white wine often
* for reds, this is everything that comes out when you open the valve - prior to pressing the rest to end extraction
Press Wine
~20% of total press for red wine
Once the free run drains off (which is most off it) - the portion that you need to press out of the skins
* red press wine is more tannic
3 press cuts for white wine?
Free Run, Light Press, Heavy Press
2 basic types of presses and which is better for quality?
Batch press (the quality option)
Continuous Press
Basket Press
Style of vertical batch press used since the Middle Ages
- grapes are loaded into basket. Pressure is applied to lid, presses down on grapes releasing juice
**pressure applied is uneven and results in low yields on unfermented berries - thus preferred for reds, not whites
Preventing oxidation during the press?
Dry ice
Sulfur dioxide
Post-Press Clarification/Solids Removal
- débourbage followed by racking/decanting the juice off
- filtration/centrifugation
- flotation - gas floats solids to top to be skimmed off
- bentonite to bind with solids
Solids inclusion increases volatile thiols and viscosity - contributes to flinty character that many call reduction. Solids contain yeast nutrients so may be included to help with fermentation and increase esters.
Methods to increase potential alcohol
- Reverse Osmosis: extracts water
- Chaptalization
*addition of grape concentrate: sugar, acid, color compounds
Methods for potential alcohol reduction
- adding water to must
- irrigating vines just before harvest
Methods to de-acidify a wine
- Malolactic conversion
- adding salts that react with tartaric salts that settle out of wine
Oenococcus oeni
Lactic acid bacteria frequently responsible for malolactic conversion
Acetic acid bacteria
Convert alcohol to vinegar. Spoilage organism.
* requires oxygen for growth/activity -thus, in damaged and botrytised fruit
*protecting the wine from oxygen by topping up and by maintaining reasonable levels of SO2 keeps the population in check
Saccharomyces
alcohol tolerant and SO2 tolerant - can finish a fermentation. Most yeasts cannot.
* low nutrient levels cause yeasts to stress and create highly reductive aromas and stuck ferments
Pied de Cuve
A portion of yeast-rich, already fermenting grape must used to inoculate - basically a sourdough starter, but for wine
Glycolysis
The 1st 10 steps of fermentation of yeasts converting sugar into energy
- evaluation of carbon
3 stages of yeast fermenation
- lag phase: yeast adapts to the high-sugar environment, little population growth
- exponential phase: building up a critical population
- stationary phase: fermentation - population is maintained until fermentation finishes and cell counts decrease
Oxygen during fermentation
Yeasts need oxygen for healthy cell walls to survive the high alc environment
* splashing, open pumpover, direct injection of air or oxygen
**no need to worry about negatives of oxidation here - yeasts ingest the oxygen immediately before it can react with wine
Low nitrogen in fermentation
Nitrogen-deficient yeasts produce hydrogen sulfide (rotten egg smell) and stuck fermentations
*YAN: Yeast assimable nitrogen
*can augment that with diammonium phosphate (DAP)
Mercaptans
bad thiols
*if not managed right, hydrogen sulfide will react to create other sulfides - methane and ethane thiols, responsible for rubber, skunk, onion smells
**aerative cap management, additional nutrients or oxygen to bolster fermentation, or copper fining can fix these
3-mercaptohexanol
passionfruit, grapefruit smells in Sauv Blanc
Yeasts’ temp range for fermentation? Most active range?
45 - 95º
mid-70’s to mid-80’s = most active
White wine fermentation temperature
Generally mid 40s to mid-60sºF
*cooler preserves more delicate aromas and crisp style. Warmer brings out more floral character + riper richer fruit
Red wine fermentation temperatures
Mid-70’s to low 90’s
*facilitates extraction from skins
*higher end of the range extracts more tannin and phenolic compounds.. darker, fuller bodied reds
Cap management
Remontage / Pumpovers
Pigéage / Punchdowns
Délestage / Rack and Return
or… submerged cap (Piedmont)
CO2 pushes grape skins up - forming the cap and separating it from the juice
*homogenizes contents of tank - essential skin to juice contact
* regulates fermentation temps by breaking up hot/cold pockets
* discourages growth of acetic bacteria
*introduces oxygen for yeast health
3 cap management techniques and their French names
- Remontage / Pumpovers: juice is pumped from bottom of tank and redistributed over top - might use sprinkler for even wetting of cap
- Pigéage / Punchdowns: mixes the tank by pushing the cap down into the liquid portion
-
Délestage / Rack and Return: liquid is drawn off and put in another container, leaving the skins in the original spot. Liquid is then pumped over top of original tank.
** most efficient, most complete mixing, and lowers fermentation temp
**or cap may stay submerged (ex: piedmont)
Cap management relationship with extraction?
More cap management = more extraction
1 -2x a day during fermentation - or 3 - 6x for bigger extracted styles
Methods to stop fermentation
- temperature
- SO2
- filtration or centrifugation which remove the yeast
- fortification with a high proof spirit
Bâtonnage
“lees stirring”
Introduces oxygen that is consumed by yeast
* re-suspends lees that fell to bottom of barrel
* during fermentation, this encourages ferment to finish
* during aging, improves mouthfeel by incorporating mannoproteins and other products of autolysis
** in general, keeps lees fresh and reduces reductive aromas
Stuck Fermentation
Stressed yeast - due to ferment temps, sudden temp change, or competition
* warming and frequent mixing keep yeasts suspended and give more access to sugar
Malolactic Conversion
- inhibitors: pH below 3.2, alc above 14.5%, low temps, sulfites
- 60 - 85º is good, 70º is ideal
- starts slow - oft lasts weeks to months
*preferable to start after primary: reduces yeast/bacteria competition, prevents stuck ferments, and malo bacteria convert sugar to VA
Buttery flavor
Diacetyl: side product of malo conversion - malolactic bacteria will continue to break it down even after conversion completes
* sulfur immediately after malo conversion preserves it - waiting til it dissipates eliminates impact
*citric acid additions: lactic acid bacteria converts citric to diacytel
Methods to stop malolactic conversion
- sulfur dioxide
- lysozyme (an enzyme that destroys LAB)
- filtration
When not intended, wine is sulfured asap following primary fermentation and is almost always sterile-filtered prior to bottling to prevent refermentation in bottle.
Timing of malolactic conversion
- after primary, unsulfered wine is at spoilage risk - some prefer to start and finish asap
- waiting allows wine to be stored unsulfed longer, aka less sulfur use overall
- for color: right after primary, anthocyanins are reacting with other compounds to create stable pigments. Malo eats those compounds - so if conversion started before color stabilized, it won’t stabilize
Micro-oxygenation
Controlled introduction of oxygen over time - can be an economical way to mimic barrel aging for tank wine
Benefits: soften tannin, stabilize color, and reduce herbaceous, vegetal, or reductive aromas
Cliquage is similar but different - larger dose of oxygen that mimics the amount you’d see with racking
Cliquage
Oxygenation technique that introduces a larger dose of oxygen that mimics the oxygen exposure you’d experience with racking
2 French oak species
Quercus robur
* coarser grain, more tannic
Quercus petraea (Quercus sessilis)
* elevated levels of triterpenoids, which contribute sweetness
American oak species
Quercus alba
* denser, less tannin, higher concentration of oak lactones, resulting in more vanilla and coconut flavors
French Oak
- species
- forests
Typically a blend of 2 species: Quercus Rober / Quercus Petraea (Sessilis)
Cool climate/less fertile soil = slow growth, tighter grain
1) Troncais
2) Allier
3) Jupilles
Medium-grain
4) Nevers
5) Bertrange
Looser-grain
6) Vosges
7) Limousin (coarse-grained, preferred for spirits)
Hungarian Oak
Zemplén Hills
95 - 100% Q. Petraea
*tight grained
Preferred oak source for spirits?
Limousin Oak - Q. Robur, coarse grains
Humidity’s relationship with wine maturing in barrel
70% humidity = water, alc evaporate at same rate
70%+ = alcohol evaporates faster, ABV decreases in time
-70% = water evaporates faster, ABV increases
Ouillage
Topping up - occurs every 2 - 6 weeks during maturation
* necessary to prevent oxidation / microbial and acetic acid growth
Alternative methods:
* store barrels on side to minimize oxidation that enters through bunghole
*open barrels as little as possible
Free SO2 vs. Bound SO2
Free: added SO2 that is avl to protect from oxidation and microbial spoilage. Highly reactive, binds to many components incl tannin, acid sugar
*wines with high RS/solids (like lees) need more free SO2 since higher proportion becomes bound
Bound: does not protect the wine
Sulfur Pre-Fermentation
- inhibits oxidation enzymes
- slows yeast growth
- inhibits bacteria
White grapes/damaged fruit typically see more. Binds quickly, will be consumed in ferment
Sulfur During Fermentation
Sulfur eats yeasts so this would only be for a specific purpose
* arrest fermentation - if RS is desired
* added immediately after primary ferment to prevent malolactic
* maintaining a certain level of SO2 is necessary for wines that are not sugar/malo dry to prevent spontaneous fermentation during aging
Racking
Soutirage
Cellar operation that clarifies and aerates wine.
* wine is transferred and settled solids (lees, etc) are left in the tank
* desired clarity, lees contact, and oxidation are considerations in deciding racking frequency
* typically racked 1x - up to 6 to mature tannin/clarify further
* “reductive” methods rack minimally and protect with inert gas in process
Scorpion
Standard test used in the US to detect brett/microbial spoilage
Stardard Burgundy barrel
Pièce
228L
Cognac vs Armagnac Barrels
Cognac Barrel = 350L
Armagnac Pièce = 400 - 420L
Champagne barrel size
205L
S. Rhone Demi-Muid size
600L
Liters in a Mosel Fuder
1000L
Bota Chica
Jerez
Shipping Butt
500L
Liters in a Jerez Butt
600 - 650L
(Bota Chica = Shipping Butt = 500L)
Liters in a Madeira Pipe
(shipping)
418L
[ Jerez Bota Chica = 500L; Port = 534.24; Marsala = 423L]
Liters in a Marsala Pipe
423L (shipping)
Caratelli size
50 - 225L
Vin Santo production
Tokay aging barrel + size
Gönc
approx 136L
Liters in standard Am. Oak Whiskey barrel
190L
Liters in standard Aussie Hogshead
300L
Cold stabilization
GOAL: reduce likelihood of crystals forming in bottle (cosmetic defect). *Standard for white wine, reds’ phenolic compounds increase solubility of tartrates so not as common
*Reduced temp = tartrates become less soluble and form crystals
METHODS:
1. refrigerate, then rack wine off tartrates
2. additives to inhibit tartrates - gum arabic, mannoproteins
3. electrodialysis
*alters acid: removal of tartrate salts decreases TA. pH 3.8 or higher increases pH. 3.8 of below decreases pH
Methods to manage Brett
- cellar hygeine
- maintain a low PH
- low RS levels
- stay on top of sulfur levels
- minimize oxygen exposure
Preventing re-fermentation in bottle
RS or incomplete malo
*sterile filtration
*SO2 addition
Methods to remove Brett at bottling
The only things that can kill it…
1. pasteurization
2. the addition of Velcorin
AND
The only thing that can remove it
3. sterile filtration
Continuous Method
Developed in USSR - used in Portugal and Germany for cheap fizz
* 5 tanks under pressure - base wine sugar and yeast go in one end to begin secondary - yeasts cannot grow under pressure and are added coninuously. Spent yeasts are filtered through tanks 2 and 3 - emerges clear after 4 and 5 tanks without yeasts
**3- 4 weeks total
French term for Charmat
Cuvee Close (sealed tank)
Charmat method
Cuvee close, granvas, autoclave
Base wines + yeast, sugar held in bulk pressure tank go under rapid ferment - ferment is then arrested by cooling wine to 23ºF when 5 atmospheres is reached
*most likely to taste like still wine with bubbles in it
Methode Ancestral
Lightly sparkling with some sweetness and sediment
* young wine bottled with some RS - ferment continues in bottle and gives off CO2
Methode Dioise Ancestrale
Twist on ancestral method. Used for Clairette de Die Tradition. Also used for Asti.
- base wines ferment in stainless steel tank at low temps over several months - filtered to remove most of the yeast, bottled, and then fermentation continues to 7 - 8.5% ABV.
- disgorged 6 - 12 months after bottlings (min. 4 months on lees) before another filtration then transferred to new bottles
(no dosage/tirage)
